For example, in a pressurized water reactor (PWR), light water is used as reactor coolant and neutron moderator to be high-temperature and high-pressure water that does not boil over the entire reactor internal, the high-temperature and high-pressure water is sent to the steam generator to generate steam by heat exchange, and the steam is sent to a turbine generator to generate electricity. Moreover, the steam generator is configured so that a plurality of heat exchanger tubes having an inverted U-shape is provided inside, end portions of each heat exchanger tube are supported by a tube sheet, and an inlet side channel head and an outlet side channel head of primary cooling water are formed in a lower end portion of a body portion. Further, an inlet portion of secondary cooling water is provided in the body portion to be located above a tube bundle shroud, a gas-water separator and a moisture separator are vertically arranged side by side, and a steam outlet is provided above the gas-water separator and the moisture separator.
In such a steam generator, multiple heat exchanger tubes provided inside the body portion are supported by a plurality of tube support plates and tube sheets. When the heat exchanger tubes are inserted into holes formed in large numbers, the tube support plate supports the multiple heat exchanger tubes to prevent vibration. In this case, the holes of the tube support plate form a special shape such that a steam circulating gap is formed between the tube support plate and the heat exchanger tube to be supported, rather than a circular shape. In this case, by broaching the tube support plate after the circular prepared holes are formed, holes of a special shape (broached holes) are formed, and on the end portions of the broached holes are chamfered. In addition, as a machining device of the holes, for example, there is a device described in Patent Literature 1.